Small enclosures for SLR digital cameras

[hfsphoto]

As a photographer who frequently shoots classical music concerts, I've built several homemade small acoustic enclosures (sound blimps) for my Nikon digital SLR cameras. My current design consists of eight inch PVC round duct with a borosilicate lens window set into a PVC flat end-cap at the front and a removable polycarbonate rear plate. There is also a concentric outer PVC sleeve and tripod mount in the center, which allows me to easily rotate the whole enclosure to accommodate both vertical and horizontal shots. The camera and lens are supported by stacks of Sorbothane disks and much of the enclosure is filled with open-cell polyurethane foam. There's an electrical shutter release and autofocus cable and lens zooming is by soft braided cords extending through holes in the PVC duct.

Now for the questions:

PVC seems to work well but is there a better material? I assume that aluminum would be good, but would require some constrained layer damping.

Should I consider a double shell, or would the reduction in volume cut down on absorption of lows in the foam? Would a rigid or limp inner shell be better?

Can I dramatically reduce the volume with a more form-fitted enclosure, or is a larger volume better?

If I continue to use plastic barriers, which attenuate best for a given mass? I've used PVC, ABS, nylon, polycarbonate and G-10 fiberglass sheets.

Thanks,
Fred

 

[GregLocock]

What are you trying to do? keep camera noise from annoying the orchestra, or isolate the camera from the orchestra?

Either way, you need to know what frequency range you are trying to attenuate.

Aluminium woud be a poor choice at 1500 Hz, for example, since in that approximate frequency range for the size you are talking about it is very resonant.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[hfsphoto]

This is an acoustic enclosure to silence the camera. Unlike the theater world, symphony orchestras don't usually have dress rehearsals in performance attire. So unless special arrangements are made, photos must me done during a regular concert with audience in the hall. Since I usually work for the orchestras or concert venues, it's especially important to be unheard by either audience or musicians.

 

[GregLocock]

OK. That's easier. So is it the shutter click and motor wind you are trying to silence?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[tomaspin]

As a confirmed photo nut, it seems like an awful lot of trouble to go to to silence a inherently noisy type of camera, whilst at the same making it pretty difficult to handle.

The main source of noise will be the reflex mirror, as there will be no film transport in a DSLR camera, so if your camera offers a mirror lock up feature ( pro film slrs can usually do this) and allows 'live view' on the rear lcd screen, then it might then be quiet enough as it is.

Another option is to use a fundamentally quiet camera - basically anything without electric motors or reflex mirrors, ie an M series Leica rangefinder would be perfect. If you want digital then an Epson RD1 body uses the M series lenses. Expensive, but very effective.

Going back to housings for your slr, could a modified underwater housing be the answer? Camera handling would be reasonable, and it might just attenuate the noise sufficiently. Standard housings are available, so you could try before you buy.

I hope this helps,

Tom

 

[hfsphoto]

Thanks Tom,

I might just go for an Epson RD1 or Leica M8 some day, but I use various lenses from 12 to 400mm, mostly f/2.8 zooms, and I don't think the rangefinders have anything good at the long end. Others have suggested point & shoot digitals, but they all have tiny, noisy sensors at high ISOs compared to SLRs. I once used an Ikelite underwater housing while diving, and it attenuates sound somewhat, but not nearly as much as a Jacobson sound blimp or my homemade enclosures. My previous work indicates that isolating the camera and lens from the PVC tube-shell with Sorbothane is very effective. Underwater housings are designed with lots of rigid connections.

Yes, the homemade sound-blimps I've made are cumbersome, but they currently allow autofocus/shutter release, lens zoom and lens-axis rotation. With very little extra work I could include focus-area selection and shutter speed/command dial access - everything I need for concert shooting.

My homemade blimps already work very well. I don't know the insertion loss, but in a quiet room the camera is inaudible from a few feet away. What I'm seeking is advice on the best barrier and absorber materials and most efficient shape for the outer shell, double wall, etc. My goal is to make a smaller, less massive enclosure and still have decent attenuation - or at least improve attenuation with my current design.

 

[hfsphoto]

Tom,

Unfortunately, I don't think any Nikon or Canon SLR digitals have manual mirror lock-up like my F4 film cameras. The interline-transfer image sensors used in SLRs work better if they're kept in the dark until the moment of exposure - so no live-view on the rear LCD screen. I'm pretty much locked into the Nikon system anyway - lots of fast glass to replace.

 

[hfsphoto]

Oops - I mixed up sensor types. Professional digital SLRs generally use full frame transfer sensors. Point & shoot digitals with live-view LCDs use interline transfer.